1. Field of the Invention
The present invention relates to a modified block copolymer which can be advantageously used for producing a polymer composition which exhibits an excellent balance of stiffness and impact resistance. More particularly, the present invention is concerned with a modified block copolymer (which is hereinafter frequently referred to as “second-order modified block copolymer”) which can be obtained by reacting a semi-modified (i.e., first-order modified) block copolymer with a second-order modifier having a specific functional group, wherein the semimodified block copolymer comprises a base block copolymer and a functional group-containing first-order modifier group bonded to the base block copolymer, wherein the base block copolymer comprises at least one polymer block comprised mainly of vinyl aromatic hydrocarbon monomer units and at least one polymer block comprised mainly of conjugated diene monomer units. Further, the present invention is also concerned with a second-order modified block copolymer-containing polymer composition which is obtained by adding the above-mentioned second-order modified block copolymer (i.e., modified block copolymer) to a thermoplastic resin and/or a rubbery polymer. The second-order modified block copolymer-containing polymer composition exhibits an excellent balance of stiffness and impact resistance. By injection molding, extrusion molding or the like, this polymer composition containing the second-order modified block copolymer of the present invention can be shaped into various shaped articles. The shaped articles can be advantageously used in various fields, such as the fields of automobile parts (interior and exterior parts for automobiles), various containers (such as food packaging), parts for household electrical appliances, parts for medical equipments, industrial parts, toys and the like.
Furthermore, the present invention is also concerned with a polymer composition comprising the above-mentioned first-order modified block copolymer (i.e., semimodified block copolymer), a thermoplastic resin and/or a rubbery polymer, and the above-mentioned second-order modifier. Also by melt-kneading this polymer composition, the above-mentioned second-order modified block copolymer-containing polymer composition can be obtained.
2. Prior Art
In the fields of sheets, films and other shaped articles which are produced from polymeric materials, there have been made a number of proposals in which there is used a polymer composition or laminate comprising a plurality of types of polymeric materials in order to obtain advantages in that a satisfactory strength is imparted to the sheets, films or the like, or the processability of the sheets, films or the like is improved, or the production cost of the sheets, films or the like is reduced. However, when producing a polymer composition by mixing different polymeric materials together, the number of combinations of different polymeric materials which exhibit good compatibility with each other, is limited. In the case of a polymer composition comprising different polymeric materials which exhibit poor compatibility with each other, a problem is likely to arise in that, due to the poor compatibility, the composition becomes non-homogeneous, and a delamination occurs between layers of different polymeric materials, thus rendering it impossible to obtain a satisfactory improving effect aimed at by using a combination of different polymeric materials.
It is well known that, as a polymeric material for obtaining a composition having excellent properties, there are used a styrene-butadiene block copolymer or a hydrogenation product thereof, and a styrene-isoprene block copolymer or a hydrogenation product thereof. However, since these block copolymers have poor compatibility with polymers having a polar functional group, such as polyamide, polyester and polyurethane, there cannot be obtained a satisfactory improving effect aimed at by using these block copolymers, and hence a useful composition cannot be obtained.
Various proposals have been made for improving the compatibility between a polymer having a polar functional group and a block copolymer selected from the group consisting of a styrene-butadiene block copolymer, a hydrogenation product thereof, a styrene-isoprene block copolymer and a hydrogenation product thereof. For example, Examined Japanese Patent Application Publication No. Hei 4-39495 (corresponding to U.S. Pat. No. 5,332,784) discloses a composition comprising a block copolymer having a modified terminal group and a thermoplastic resin. Unexamined Japanese Patent Application Laid-Open Specification No. Hei 7-173390 discloses a composition comprising a polyamide resin, a graft copolymer comprising a hydrogenated block copolymer having a polyamide grafted thereon, and a hydrogenated block copolymer having bonded thereto a specific amount of an unsaturated carboxylic acid or a derivative thereof. Unexamined Japanese Patent Application Laid-Open Specification No. 2000-219800 discloses a composition comprising a polyester resin, a polyamide resin and an epoxidized block copolymer. Unexamined Japanese Patent Application Laid-Open Specification No. 2001-55492 discloses a composition comprising a polyester resin, an epoxidized block copolymer, a multifunctional compound and a polyether-ester elastomer.
On the other hand, as a method for producing a block copolymer having a functional group, Unexamined Japanese Patent Application Laid-Open Specification No. Sho 59-98106 (corresponding to U.S. Pat. No. 4,465,809) discloses a method for producing a carboxyl group-containing polymer, in which a polymer-alkali metal composition is contacted with an epoxy compound, and the resultant product is directly contacted with a cyclic, acid anhydride, thereby obtaining a carboxyl group-containing polymer. However, such carboxyl group-containing polymer (which has a terminal epoxy compound residue having bonded thereto a cyclic, acid anhydride residue) has poor affinity to a thermoplastic resin and/or a rubbery polymer, an inorganic filler, and the like.
Unexamined Japanese Patent Application Laid-Open Specification No. Sho 63-238107 (corresponding to U.S. Pat. No. 4,972,023) discloses a polymer which is modified with a terminal acid group (or a salt thereof) which is bonded to the polymer through an acid amido group, and discloses a method for producing the modified polymer as well as applications for the modified polymer. This modified polymer is obtained by a method in which the modification is performed using 1,5-diazabicylo[3.1.0]-hexane and a derivative thereof and a Schiff base derived from an aliphatic or aromatic amine and aldehiyde. The modified polymer (which is modified with a terminal acid group (or a salt thereof) which is bonded to the polymer through an acid amido group) has poor affinity to a thermoplastic resin and/or a rubbery polymer, an inorganic filler, and the like.
Thus, in the prior art, no composition has been obtained, which comprises a block copolymer comprised of vinyl aromatic hydrocarbon monomer units and conjugated diene monomer units, and a thermoplastic resin and/or a rubbery polymer and which exhibits an excellent balance of stiffness and impact resistance.